MMPR: Zach/Black Ranger (Always loved him. Always superior to fan favorite Billy and Tommy. However, I'll be fair and admit that I've had a soft spot for Tommy as the Green Ranger)
MMPR S2&3: Adam/Black Ranger (Come on. How can you not love Adam?)
Alien: Delphine/White Alien Ranger (I guess?)
Zeo: Jason/Zeo Gold (Jason was a cool dude, but he became so much cooler when he returned)
Turbo: TJ/Turbo Red (TJ is one of my favorite rangers of all time. People need to stop being so critical on Turbo after passing dumber bullshit for MMPR and Zeo)
In Space: Andros/Space Red (I love TJ in this series, too. But Andros was pretty cool)
Lost Galaxy: Kendrix/Galaxy Pink (How many rangers have been willing to make the ultimate sacrifice? Probably all, but only one proved to actually do it)
Lightspeed Rescue: Carter/Lightspeed Red (Always willing to pull the trigger)
Time Force: Tie between Jen/Time Force Pink and Eric/Quantum Ranger (Both were absolutely cool. Jen's story throughout the series made me love her, but Eric being the first "Brash" ranger made him more interesting than many of his predecessors)
Wild Force: Merrick/Lunar Wolf Ranger (He was kind of the only interesting one in the team)
Ninja Storm: Eh, none of them, really. I guess Cameron/Samurai Ranger
Dino Thunder: Trent/Dino White (I'm not really big on this series. They were all "Alright" at best. Trent was kind of interesting, though)
SPD: Bridge/SPD Green (I love a lot of the SPD Rangers. Jack, Skye, Z, and Doggie all had a good chance, but the amount of fun and energy Bridge brings is enough for me)
RPM: Ziggy/RPM Green (Gotta love the guy)

Can't comment on Mystic Force, Overdrive, and Jungle Fury since I don't remember them much. Only watched half of the Neo Saban era series.

MMPR: Red ranger Jason
Zeo: Zeo Ranger Four Green Adam
Turbo: Turbo Red Ranger TJ
In Space: Pink Space Ranger Cassie
Lost Galaxy: Red Galaxy Ranger Leo
Lightspeed Rescue: Red Lightspeed Ranger Carter
Time Force: Quantum Ranger Eric
Wild Force: White Wild Force Ranger Alyssa...I guess. I didn't really like this cast or season
Ninja Storm: Six way tie. I loved them all. In Space is my favorite season, but this cast was great
Dino Thunder: Blue Dino Ranger Ethan
S.P.D.: SPD Yellow Ranger Z. Also, I still have a crush on her. Monica May is my jam.
Mystic Force: Solaris Knight Daggeron
Operation Overdrive: None. At all.
Jungle Fury: Jungle Fury Wolf Ranger RJ. Also one of the best mentors, if not the best. I almost picked Dominik, but only because the actor was in Daredevil lol
RPM: Ranger Series Red Scott
Samurai: Samurai Red Ranger Jayden. I think he was the most fleshed out ranger in a copy-and-paste season. Also, I enjoyed how he was willing to trick a kid with a vision and make sentient clones to die in his place. He could make all the hard decisions.
Megaforce: Robo Knight, by default.
Super Megaforce: I guess still Robo Knight here. None of the other rangers were fleshed out. I wanted to pick Gia, but all we were told about her is that if you creep on her long enough she will give in and date you. A phoned in Robocop was the best thing this season had to offer in terms of rangers. Noah was a close choice, but his development made little sense between the seasons. That is at fault of the hybrid season though.
Dino Charge: Dino Charge Pink Ranger Shelby

MMPR: Billy, who showed that geeks can be badasses.Zeo: Billy, who was probably one of the most effective Mission Controls in PR history.Turbo: Uh... I don't know. I didn't hate Justin and TJ was pretty cool.In Space: Zane. Dude had style. (TJ would count but I used him for Turbo)Lost Galaxy: Never watched it.Lightspeed Rescue: Carter, because there's no other right answer.
Time Force: Can I count Wes, Jen, and Eric as one character? They all kind of had intermingling plot lines (usually via Wes).Wild Force: Merrick, I guess. Wolves and all.Ninja Storm: Cam. See: Billy.Dino Thunder: ... I honestly can't remember the names of anyone other than Kira and Trent.SPD: Skye. His dedication to duty, his dream to carry on his father's legacy, and overall strong development from being simultaneously arrogant and by-the-book into a flexible, practical leader earns all the points.Mystic Force: Didn't watch it.Overdrive: The font for the end credits.Jungle Fury: RJ, I suppose.RPM: AH'M SCOTTISH!MMPR Redux: BillySamurai: Kevin by default.Megaforce: Robo Knight. Odd that the machine had the best acting.Dino Charge: Kota.